energy ◦ the ability to do work or cause change ◦ occurs in various forms ◦ can be converted...
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Chemical Reactions and Enzymes
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Energy ◦ The ability to do work or cause
change◦ Occurs in various forms◦ Can be converted to another form◦ Forms important to biological
systems are chemical, thermal, electrical and mechanical energy
◦ Free energy is the energy in a system that is available for work
Energy and Matter
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Atoms are in constant motion The rate at which atoms or molecules in a
substance move determines its state
States of Matter
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◦Solid Molecules are tightly linked. Little energy
◦Liquid Molecules are not as
tightly linked Medium amount of energy
States of Matter
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◦GasMolecules have little or no attraction to each otherFill the volume of the occupied containerMove most rapidly
To cause a substance to change state, thermal energy (heat) must be added to or removed from a substance
States of Matter
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Living things undergo thousands of chemical reactions as part of the life process
Energy and Chemical Reactions
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Many are very complex involving multistep sequences called biochemical pathways
Chemical equations represent chemical reactions◦ Reactants are shown on
the left side of the equation
◦ Products are shown on the right side A + B C + D
Energy and Chemical Reactions
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Much of the energy organisms need is provided by sugar (food)◦ Undergoes a series of
chemical reactions in which energy is released (cell respiration)
The net release of free energy is called an exothermic reaction
Energy Transfer
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Reactions that involve a net absorption of free energy are called endothermic reactions
Photosynthesis is an example
Energy Transfer Mix Barium hydroxide and aluminum salt, and the products dissolve in water of hydration. This is VERY COLD!
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Most chemical reactions require energy to begin
The amount of energy needed to start the reaction is called activation energy
Energy Transfer
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Certain chemical substances (catalysts) reduce the amount of activation energy required
Biological catalysts are called enzymes
Catalysts
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Enzymes are an important class of catalysts in living organisms◦ Mostly protein◦ Thousands of different kinds◦ Each specific for a different chemical
reaction
Catalysts
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Enzymes work on substances called substrates
Substrates must fit into a place on an enzyme called the active site
Enzymes are reusable!
Enzyme Structure